Under requirements of high-speed and high-traffic wireless communication, working frequencies of a communication system are becoming higher and higher and working bandwidths are becoming larger and larger. A local frequency source having a high working frequency in a system is facing a great challenge. Therefore, a frequency multiplier (especially a frequency multiplier having a simple structure) is widely used to increase a working frequency band of a frequency source. However, a conventional frequency multiplier has a problem of being unable to suppress an even harmonic wave.
A solution using a frequency multiplier with discrete element design has been proposed. The frequency multiplier is a frequency synthesizer circuit with double-ended input and single-ended output. An electrical length of every branch transmission line is an integral multiple of one half wavelength corresponding to a reference working frequency. The electrical length of the transmission line is adjusted to output a resonance point corresponding to a load, so that the entire circuit works with a multiplied frequency of the reference working frequency, thereby implementing frequency synthesis.
However, the conventional frequency multiplier is capable of outputting only one frequency multiplied signal and cannot output differential signals.